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Helicopter flight: Does the rotor disc plane and hub plane rotate along axis perpendicular to rotational axis?
In many pieces of literature, diagrams as below are shown to explain the directional flight of Helicopter. I have the understanding that the cyclic input will only change the pitch angle of the blades and hence the amount of lift forces acting will vary around the disc. BUT the disc-plane (more specifically, the hub plane), will remain parallel (to the reference plane, for example, the skids, or the top surface of the helicopter). I mean, the disc plane shouldn't pitch down or up as shown in the diagram.
Am I correct? Also, I am finding hard to give a suitable name to the "reference frame", I tried to define above. Is there any standard name for that?

The shaft does not tilt, but the disk does.
You understand the function of cyclic control correctly. It indeed changes the pitch of the individual blades, shifting the centre of lift.
However, the blades are not strong enough to take that much bending load. If the rotor was completely stiff, they'd quickly break off. So instead the blades are allowed to flap up and down. That allows the plane of rotation of the blades to change first when you apply cyclic input and the body attitude follows.
The body attitude follows. When the rotor tilts, the action like of lift gets tilted with it, so it no longer passes through the centre of gravity, which will create a moment that will try to pull the body into the attitude corresponding to the rotor. With individual flapping hinges or flexing there is additional, more direct torque on the rotor hub trying to do the same, while on teetering rotor this is the only effect and the way cyclic is rigged prevents the rotor from trying to tilt too far relative to the body.
See also How are pitching and rolling moments transferred from rotor to the body?

Thanks. So, I believe what I should have used is - hub plane, instead of a disc plane. Am I correct in understanding that the hub-plane doesn't move (pitch down or up)?

@RajArjit, the hub indeed does not move. Though on teetering rotors the hub is just a hinge on which the pair of blades teeter—that mechanism is simpler, but it does not transfer any torque to the body, which makes it prone to ‘mast bumping’ when the rotor is unloaded.

thanks. I understand now.

this video suggests that the hub moves by lot. https://www.youtube.com/watch?time_continue=9&v=tO0sRWCf9k4&feature=emb_logo Please let me know what I am missing.

@RajArjit, the video is so blurry and poor resolution that it does not suggest anything at all.

The blades are hinged near their roots, so they have some degree of freedom, and they flap up and down, so that the disk defined by the path of the blade tips is almost always at an angle with respect to the plane perpendicular to the rotational axle.

I understand that. Does the hub always remain at zero angle to the plane perpendicular to the rotational axle?

Raj, the diagrams you have submitted are correct. There is no movement of the main drive shaft other than rotational. The disk (blades) tilts as a result of flapping hinges (flapping occurs whether it’s a fully articulated or rigid rotor head) receiving a control input from the swash plates. The swash plates, one rotating & one non-rotating, turn pilot control inputs into the blade movement which is controllable in any direction.


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What are the missing elements to mandate airliners to have an AoA indicator?

ONGOING EDIT NOTE (By OP) This question is right now being comprehensively reworked to make it less broad over the course of the next number of days. (That's being done mainly offline, so as to offload version management). If you are interested in this question, I welcome you to leave a comment or some in the meantime and check back later.
EDIT NOTE: (By OP) [previous and ongoing] The text of this question was changed comprehensively to correct formal issues while taking care not to break coherence with previously given answers. I explicitly own any issues in that quarter.

Original title (for reference only): Why are aircraft manufacturers even permitted to sell aircraft without an AoA indicator?
Owing to that, answers are definitely not out of scope that cater to whether seeing an AoA indicator as important enough makes sense in the first place.

tldr
Given the work done and published by regulation authority in the last two decades, what are the missing elements to forbid airliners without AoA indicator to be sold?
// Soft back edge of second rework pass here //
An AoA indicator is arguably a relevant piece of equipment on a flight deck. Despite recommendations in widely followed accident reports towards mandating its presence in aircraft, little has generally happened in that quarter since, and with observable reluctance in some cases.
This could suggest to suspect that something may be missing from the statutes or reality of the regulations and procedures that one might expect to be sufficient to cause aircraft manufacturers to follow suit.
Whether or not the suspicion holds (which might or might be opinion), this question is interested (not in whatever possible opinion but) in looking at the elements that the relevant procedure consists of and learning whether the relevant procedure has missing elements or elements that are establishably too weak to effect AoA indicators to be mandated.
( I am interested to know what elements ... ) // WIP - EDGE of second rework pass here //
As a side effect, I expect to potentially learn something about regulations in general (as all regulations can't have been made just because of AoA :D)
Evidence to consider
// WIP - Another EDGE of second rework pass here //
[ outline: 1. AoA (science, more or less: (theory), practice, accidents) -> 2. Recommendations (implement) -> 3. Effect (generally none or not from 2.) -> 4. opposing forces (anecdotically visible: press)  -> 5. elements of procedure (a. generally capable in terms of process b. capable of overcoming 4.) (or lack thereof, either in elements' existence or capability) ]
[ As far as opinion is concerned, it may be unfathomable and thus left to opinion whether element X in procedure Y is apparently not acting strongly enough in case A to overcome resistance Z and accomplish result R. But it is presumably possible (and I think not opinion) to establish whether a procedure Y: (S1->S2) to move a matter from state S1 to state S2 exists in the first place and whether Y contains elements Xk such that S1--[(all(Xk))]-->S2 is at least theoretically sound and can logically be expected to work. We could then explore (where necessary) which Xk are counteracted by Zj and whether all Xk are (and have been successfully) designed to overcome any respective Zj - or, OTOH, designed (or "somehow" become) such that overcome(Xk,Zj) could provably not work or reasonably be expected not to work ("is too weak to effect", "is incapable of insuring" etc.) Sort of like the logic about moving control surfaces - no hydraulics, no move.
NOTE: Question will then not cover such reasons for 3. as are NOT procedure but are e.g. such as "the procedure was all set but nobody cared" or "Politician P just didn't wish to inconvenience manufacturer M into complying" - unless that's a matter of clear evidence and has been thoroughly established outside this network. Or maybe not even then, as the question will need to be narrowed down to something like procedure. Other stuff might be content matter for another question. ]
old tldr
This question asks about regulations and procedures governing aircraft design and implementation. As it was originally prompted by looking at a prominent example of an aircraft design element that got recommended for consideration to implement by a governing body (which still didn't happen), the question looks at that example only as some sort of anecdotal background and, well, example (which may in itself be open to opinionated discussion). The question, however, is about factual properties of the regulations and processes governing the field that e.g. the example exists in, both as set down and as observed in reality (not strictly restricted to the example).
So a governing body recommended looking at making this feature mandatory, then although that means something, it didn't happen. So what are the properties of how regulations are and work that facilitate deviating from such recommendations, what influences are at play and how do the processes work that result in the application of regulations as well as the changes that regulations and processes are subject to themselves.
Angle of Attack
The Angle of Attack (AoA) of an aircraft in flight is a well-known critical element of a stable flight attitude. Correctly observing AoA corresponds directly to flight safety and arguably to the relative effort and ease of maintaining this aspect of flight safety -

No matter your weight, if you fly at the right AOA you’ll have the right stall margin*

On a side note, it interestingly also corresponds to flight economy in a way recently discussed in more detail here (ibid.)

[this] angle of attack ... represents the most efficient way to fly [at that chosen optimum]
[Source:] "Low-Cost Accurate Angle-of-Attack System", Borja Martos and David F. Rogers, Journal of Aircraft 2018 55:2, 660-665

*)  (I won't nitpick whether and how airspeed should have been mentioned along with it)
Angle of Attack indicator
Based on these observations, there is arguably ground for considering whether it makes sense for aircraft to be equipped with instrumental indication of Angle of Attack on the flight deck (AoA indicator [1]), or whether that should perhaps even be mandatory, based on the importance of AoA for flight safety as indicated in investigations.
*On a purely textual note, "AoA" in this question will be used to mean "Angle of Attack" but I seem to recognize that "AoA" can sometimes be used to mean "Angle of Attack indicator" as well, depending on context. As for this question, please feel free to edit in case there's a problem with that.* [1] [rather broad, better illustrative source welcome]
Background in aircraft accidents
While there has been quite considerable argument about the ifs and hows of the actual necessity and usefulness of having an AoA indicator on the flight deck, investigation into a number of aviation incidents turned lethal accidents, such as AF447 stalling into the Atlantic Ocean, and the more recently Boeing 737MAX crashes, has suggested that it might have helped to avoid the fatal outcome of these events if the respective aircraft had been equipped with an AoA indicator.
For quick reference, Flight AF447 avoidably crashed out of a sustained pilot-induced stall that went unnoticed or misinterpreted, aggravated by other factors. The aircraft did not feature an AoA indicator. In the 737MAX crashes, again flight crews had no indication of the aircraft's AoA available to help in mitigating the avionics' acting up following internal disagreement about the aircraft's AoA (which it obviously did measure but was not designed to display, such as on the glass panel).
After each of these accidents, (non-) indication of AoA was discussed as an arguably relevant factor in the sequence of events leading to the respective crash. The more recent events led to the aircraft manufacturer eventually adding a proper AoA indicator into the glass panel PFD on the Boeing 737MAX. The same action was not taken in the type of AF447, the Airbus A330. (Sources as given above.)
In section 4.2.2 of the AF447 investigation final report, the BEA as the investigating body recommended

that EASA and the FAA evaluate the relevance of requiring the presence of an angle of attack indicator directly accessible to pilots on board aeroplanes

However, this has apparently not led to broad adoption, much less to a making mandatory of AoA indicators, though some have been lately appearing in some aircraft (as mentioned above) on an arguably less mandatory basis.
After investigation into the 737MAX accidents had started showing that an AoA indicator would have been vital in identifying and changing a sequence of errors leading to at least one of these massively fatal crashes, the manufacturer could be observed in the market as having an AoA indicator for the aircraft type more or less ready for delivery but was apparently fighting to not deliver it to customers unless they paid a presumably significant upgrade price for "options".
While that may be understandable from a (ethically agnostic) purely monetary perspective as designing and actually building an AoA indicator into an aircraft arguably costs money, practically withholding from flight crews a potentially crucial instrument - which was the reported effect in a number of less deep-pocketed airline operators - motivated the original wording of this question: Why are transport aircraft manufacturers, or any aircraft manufacturers and designers, for that matter, even permitted to build and sell aircraft with no AoA indicator built into the flight deck as a standard item?
While that original take drew opinion, the more factual point this arguably seemed to point to was problems about regulations and procedures and what would be happening with respect to them in (the cruel?) reality.
Question (revamped)
This question now asks for insight about the general aspect of regulations and processes, both in place and actually used, to ensure flight safety based on aircraft design and the parameters of operation to go from there.
The issue of whether aircraft generally are, and should be, equipped with an AoA indicator, may serve as an example of issue and application.
I would like to gain insight primarily focused on contemporary commercial transport - and possibly GA - aircraft over the last 40 years or so to present.
Broader insight into issues found in the topic, being of a more general nature or reaching further back in aviation history, will be welcome within the reasonable necessity of not letting the question get to broad.
I am less interested in the matters of opinion already mentioned, rather in the properties of the processes involved with the inception and outcome of aircraft regulations. Insofar as there exists opinion that hasn't already been mentioned, I'll be happy to be pointed to the existence of such opinion or discussion for more insight, but still:
the subject of this question is about hard facts about regulations and processes concerning the aircraft industry in creation, delivery and use of its products, and how these regulations and processes have been (and are being) developed and applied in reality and how this plays out.
To be sure I'm not asking about speculation, albeit such speculation may be mentioned as existing in an answer for illustration. I am interested in the way regulating the aircraft industry for equipment and safety issues works.
Answers might point to relevant aspects of how both set-down and real-life procedures in regulations are put in place and executed and how these procedures observably are followed and play out.
Such as, what would it mean for the regulations and procedures to be worked and developed "right by the book", what influencing factors and deviations would be encountered, and how would the procedure building and executing process go about deviations to mitigate the effects of ill influence or eliminate it/them as far as that is possible.
In the face of an AoA indicator apparently still not being a standard feature of an advanced aircraft at present, but being reported to appear in some aircraft for arguably different reasons (which may in itself be beyond the scope of this question), I would be interested to know

what became of the BEA's recommendation,
how does that relate to how regulations and procedures work (or how they should be working and how things do play out in reality)
what would one expect about regulations and procedures working the way they should (and what would that be in the first place)
if this AoA issue is indicative of anything, would this be a typical case of what happens (or can happen) or (observably) rather an edge case

I am not asking about opinion on these points but about observable properties of e.g. regulations typical of governing the procedures used in establishing the design of aircraft and what they are explicitly made out to effect (think of must, shall, should and what is being unambiguously mandated or aimed at, and of compliance observed in reality and how that gets handled, end-to-end.)
and more generally, as far as the scope of the question may go without being too broad, how are regulations and procedures in the aircraft industry developed and applied after all with respect to issues relating to critical equipment.
I particularly welcome insight into how money and other unilateral or colluding interests come into play and how do regulations act and develop to mitigate the effect of such interests.
With respect to the established processes in developing and getting approval from authorities for an aircraft design, I wonder what properties of the overall process and its surroundings would be capable of leading to some safety-critical decisions about aircraft equipment being left to the unilateral considerations of aircraft manufacturers. (capable of meaning obvious capacity not opinion. This should be verifiable by e.g. whether it could possibly happen in context i.e. other properties of reality not precluding it etc., and going from there, if there are cases where that has clearly happened, potentially also cases (fact) where it arguably happened (then, I take that whether it did and whether that was due to it being possible in the first place because, would be opinion - the mere existence of it would be again fact and could be noted - but the fact wouldn't.)
Historically (and currently), if one were to assume that an AoA indicator should be mandatory in an aircraft, just for the sake of making observations, then, have other comparable safety features or measures seen the same predicament (or have been known to are viewed this way by some)?
What properties of the regulations and processes used in the last decades as implemented in reality have allowed the state of affairs to become what it is, and in case changes to that have been discussed, what became of it?

I feel this question would bring opinion. Note that many equipment you can find today on airliners (I think your question is restricted to airliners but you should explicit if this is the case) didn't exist when the first jet airliners were certified. Then it is not  surprising that compulsory equipment are added little by little to new aircraft types.

In case of the AF447 the AOA would have shown 40° or so and the pilots would have thought it was a sensor error. And in the B737 Max crashes the AOA indicator would show a high value that doesn't change, so again not useful for the pilot.

While I personally agree about AoA usefulness and desirability, I must say that its presence on every Soviet airliner didn't make them enjoy much better safety record, even with respect to stall-related incidents.

@Jan is correct, the problem wasn't one of instrumentation or information available to the pilots, it was that they were fitting their problems into the wrong model of their situation

I hear you @Manu H and have done so from the moment I first saw it but still I do beg to contest the closing as opinion based. While there may be some elements to opinion, that's not the center of gravity of the question. Please note the parts asking about process, both technically and historically. Dean F is addressing that briefly saying that regulations move slower than the technology they regulate. I read in another place (don't remember exactly where now) regulations are written in blood. Respectfully, there could be more in terms of answers without first having to close and re-edit.

Sorry I was going to edit my previous comment to state correctly that @Dean F is mentioning regulations are written in blood (I somehow couldn't find that again though I did look and use in-page search too) but I got hit by that restriction saying comments can only be edited within 5 minutes. That said, this regulations and blood thing alone seems, to me, to make for a whole lot of history to mention. Which emphasizes my point.

@somebody_other I'm not the only one involved in the closing process. The closing and reopen mechanism is here to enforce quality. A good way to orient the question would be to ask about the results of the evaluation recommended in section 4.2.2 of the AF447 investigation final report

@ManuH just pinging to say thank you for your kind suggestion and encouragement. Finally got around to applying it and this is about as good as think I can do right now. Cheers

@ManuH (and also whoever did this) thanks again but I guess I have just learned that putting in any effort is not worth it whatsoever unless one is already high-rep (Just received another inscrutinably motivated downvote) Oh well...

That... is a lot of text! I understand you're trying to refine the question so it can be reopened, and I applaud you for your efforts - sometimes it's not easy. Unfortunately, from what I'm reading now, this is likely too broad: "This question now asks for insight about the general aspect of regulations and processes, both in place and actually used, to ensure flight safety based on aircraft design and the parameters of operation to go from there." could take an entire book to answer...

@somebody_other If I were you, I would abandon this question, even delete it to not impact your reputation due to downvotes (BTW, I didn't downvoted) and ask a fresh new one. You now have a better overview of how you can orient the question to avoid "to broad" or "opinion-based" and what specific aspect of this wide problem you now what to have information about.

@ManuH theoretically speaking that's a no-no. Also, not properly the best choice for OP. Deleted downvoted question weight against the account from the perspective of the automated housekeeping algorithm.

@Federico I fear continuing editing this question make is less clear as it must not invalidate the current answers and some good editing can make the current answer partially off-topic.

@somebody_other I'm still trying to find a shorter title that sums up your idea but I can't find better than "given the work done and published by regulation authority in the last two decades, what are the missing elements to forbid airliners without AoA indicator to be sold?" but I'm still unhappy with that (otherwise I would have edited the title myself)

@ManuH you just made my day! That's something I can go from (to be seen in a minute). Then remains the chore of reducing that lot of text to a better length. I'll have a go at it asic...

@Federico Thank you for the heads-up. I already once drew that (outing?) "Peer Pressure" badge (from being a bit rash or unclear at that one time, sorry). Wondering anyway whether that's what earned me "cant post on Meta without 5 rep from SO" (where I'm just not active right now). I guess I can do without renewing the experience.  About editing, ManuH precisely nailed it. I'll give the text another try when I can.

@somebody_other no, the 5 rep limitation is for every new user on every site.

While your argument for the inclusion of AoA Indicators is insightful, there are a few things to take into consideration. Namely, that regulations move slower than the technology they regulate. The basic cockpit instrument panel equipment that every powered aircraft (big or small) is required to have is regulated in the FAR/AIM by Part 91.205. Stall warning devices and AoA devices are not required equipment. To make them required would require a change in the regulation. The way stall warning is achieved is regulated in Part 25. Part 25 does not require a device, instrument or indicator though one is possible as supplemental. Warning can be achieved by aerodynamic buffeting.
§25.207 Stall warning.

(a) Stall warning with sufficient margin to prevent inadvertent stalling with the flaps and landing gear in any normal position must be clear and distinctive to the pilot in straight and turning flight.
(b) The warning must be furnished either through the inherent aerodynamic qualities of the airplane or by a device that will give clearly distinguishable indications under expected conditions of flight. However, a visual stall warning device that requires the attention of the crew within the cockpit is not acceptable by itself. If a warning device is used, it must provide a warning in each of the airplane configurations prescribed in paragraph (a) of this section at the speed prescribed in paragraphs (c) and (d) of this section. Except for the stall warning prescribed in paragraph (h)(3)(ii) of this section, the stall warning for flight in icing conditions must be provided by the same means as the stall warning for flight in non-icing conditions.
(c) When the speed is reduced at rates not exceeding one knot per second, stall warning must begin, in each normal configuration, at a speed, VSW, exceeding the speed at which the stall is identified in accordance with §25.201(d) by not less than five knots or five percent CAS, whichever is greater. Once initiated, stall warning must continue until the angle of attack is reduced to approximately that at which stall warning began.

Another consideration is that as technology advances, aircraft equipment requirements will change. This will be predicated on the perceived value of the equipment to improve safety. The old saying is that regulation are written in blood. The more deaths from a particular cause, the more regulation will be enacted to prevent the cause.
Unfortunately, more technology does not fix many of the root causes of accidents. For instance, stall indicators such as stall warning horns and AoA indicators will not prevent accidents in the case of: sensors supplying the information being misaligned, damaged or inoperative; instruments being faulty; instruments giving incorrect information; the information given being ignored, misinterpreted, excluded from importance, fixated upon, or unnoticed due to over saturation of information. Some of these issues could be considered as unavoidable or acts of God. Others can be considered under the category of manufacturer, maintenance, or pilot error. The accidents that you noted might or might not have happened with or without an AoA indicator. Ultimately, pilots must be able to fly the aircraft with less than even the basics of equipment in 91.205. First and foremost, the pilot has to understand their aircraft and its limitations. No new equipment will fix or change that simple fact. Especially, when things start to go wrong.
If you are a pilot, you may understand the concept of task saturation. It is like juggling. Juggling one ball is not even juggling. Juggling two is easy. Juggling three is a skill. As you continue to add balls, the task of juggling gets harder and harder. If you add one more than your max, the tendency is not to drop that one or a different one ball. All of the balls fall.
At some point, adding another piece of information to the PFD is counterproductive. There is not enough real estate on the screen nor in the pilot’s conscious mind.
If the pilot has visual reference to the horizon an AoA indicator is superfluous. If the pilot does not have a visual reference to the horizon, the Attitude Indicator will substitute for the absent natural horizon. If the Attitude Indicator is faulty, cross referencing the other instrument will substitute for the Attitude Indicator. If the pilot gets too task saturated to take in all of the above information, the stall warning indicators should warn them of an impending exit of the normal flight envelope. If the pilot has to rely on the proper function of every and all equipment plus one more, then we have a bigger problem in aviation than the equipment list.
If you are not a pilot, maybe this example can sum up the last few paragraphs. The AoA Indicator is like the low fuel warning indicator in your car. The low fuel warning works off of the information from your fuel gauge. Your fuel gauge has to work properly for the warning to work properly. But, if you are an attentive driver, it should not take a low fuel warning for you to know that you are low on fuel. For a responsible driver, the low fuel warning should never come on. An exceptional driver should not even need the fuel gauge. They would just fill the car’s fuel tank after a certain amount of use taking into consideration a margin for/of error. Yet, we still have people run out of gas even in cars with low fuel warning indicators.

"horizon an AoA indicator is superfluous" I presume you mean "attitude indicator" not "AoA indicator"?

@FreeMan - I see your point. But, no I meant the AoA is superfluous. The AI is a convenience when VFR. Neither is necessary. I like having the AI at night. Although, both can be a distraction. I’ve had the AI go out in flight a couple of times in VMC day & night. I’ve had to cover the AI with a sticky note to keep from fixating on it even though my conscious brain knew that it was not operable. The few times I’ve flown with AoAs, I’ve actually found them annoying when doing slow flight and intentional stalls.

and... that's why I didn't edit. :) However, (remember, IANAP) if I can see the horizon, how does that negate my need for an AoA indicator?  Also, since you go from there into talking about the AI, it's confusing...

@FreeMan - Don’t get me wrong. I love the idea of an AoA. I love technology in general. I don’t think we should rely solely on it. It’s just a useful tool when used correctly. It’s a danger when not used correctly. If I have allowed complacency to set in, and I am ignoring what the aircraft is telling me, the AoA might save my bacon. Hopefully, I won’t let things get that far. And, help me remember IANAP. I am drawing a blank right now.

I Am Not A Pilot. I'm not suggesting you're not for an AoA, I guess I'm just confused by how a visual reference to the horizon makes the AoA superfluous. It's my understanding that a visual to the horizon makes an AI superfluous.

@FreeMan - On a clear day, a pilot can fly an airplane without an AoA, Attitude Indicator, Vertical Speed Indicator, Directional Gyro/Heading Indicator, GPS, and/or navigational radios. They are nice-to-have items only. When the weather turns to IMC, all but the AoA, VSI and GPS become necessary and required. A pilot is prohibited from taking off IFR without them. A pilot should still be able to fly the aircraft if some of those become inoperative midflight. There are some very useful tools which are not required for flight (ADS-b in, GPS, EFBs, handheld navcom, etc). I still like to have them

@FreeMan - On a clear day, a pilot should spend 90-95% of the time looking outside of the aircraft instead of looking at instruments. The most important tool is their eyes. The engine gauges actually become more important than the AoA, AI, VSI, DG/HI and Turn Coordinator (I neglected to add this one to my original list). Some aircraft do not have these items and were never designed nor intended to have these items. I, for one, prefer to fly with them operational in the aircraft. Especially at night. Even though they are Superfluous (def: unnecessary, especially through being more than enough).

@DeanF. thank you very much for your thorough answer and the kind way you gave it. Accepting your answer now, you have helped me learn a lot. I was going to do this a number of days ago already (and should have).

You ought to edit the title to actually be a question.

adding another piece of information to the PFD is counterproductive interestingly, I recognize I never imagined the AoA indicator as part of the scan, just as something to throw a look at when something acts up or turns incomprehensible (such as getting in on what the MAX is thinking it's doing, or might I have reason to believe I'm overlooking something, like on AF447). I guess I'd generally prefer to fly by just as little instrumentation as needed to be in the loop and be the ball (as that UA instructor (IIRC) I think aptly put it).

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How is CAS ans GS affected by instant wind changes at different altitudes
Okay, a theoretical example here which I hope will help me understand the physics better.
Conditions:

Altitude: 50 ft (over sea)
GS: 300 knts
CAS: 300 ktns
Wind: 0

If I now get a 10 knts head wind (instantly) which will keep constant at 10 knts. Will it result in GS = 290 and CAS constant at 300? Will my CAS at first jump to 310 and then go back down to 300?
What would happend if I get 10 knts direct tail wind, will it still only affect the GS by in this case increase it to 310?
Is this true for all (within reason) altitudes?

@Bianfable I mean CAS.

@Bianfable Thanks, I updated the question.

Aircraft fly relative to the surrounding air. If your aircraft is trimmed to fly at a certain airspeed, and the airstream changes due to wind or other factors, the aircraft naturally returns to its trimmed flight state and speed relative to the atmosphere. For this reason the groundspeed is the vector subtraction of your velocity vector and the wind speed.
With this in mind, you can see that your second statement is correct

Will my CAS at first jump to 310 and then go back down to 300?

Your example plays out like this: You fly at 300 knots (airspeed and groundspeed, hence wind is 0), suddenly the wind increases, and because of conservation of momentum you will not immediately slow down, therefore you will read 310 knots on your airspeed indicator. However because your airplane is trimmed to 300 knots, you will slowly decelerate until you airspeed is decreased to that value. Because of this deceleration, your groundspeed will have decreased accordingly by 10 knots to 290 knots. For me it helps to imagine that you fly by pushing against the airmass surrounding you, therefore if the whole airmass around you goes backwards, so do you (by 10 knots).
In the case of a tailwind, the whole situation is reversed. When the tailwind hits your aircraft, first you will fly only 290 knots (again because your aircraft conserves its momentum), and then your aircraft accelerates to return to its trimmed flight speed of 300 knots. At that point your groundspeed likewise accelerated to 310 knots.
This is true for all airspeeds. There is no altitude dependency, especially if you do these calculations with TAS.

The same principle also applies for cross winds. This is why, (contrary to generally accepted understanding), when taking off in a strong crosswind, if you apply the appropriate cross controls (downwind rudder and upwind aileron), to control aircraft heading on the runway, and release these controls immediately after liftoff, the aircraft weathervanes into the wind, and, as it accelerates, moves upwind from runway centerline, not downwind from the the wind pushing it, as is sometimes postulated.

@CharlesBretana - alternate scenario - consider a light airplane that will not accelerate a great deal between liftoff and reaching desired climb speed, but will climb up through the wind gradient into a stronger crosswind--

Yes, you're right, that changes things. But perhaps not as you might surmise, (if I read your intentions properly). For the sake of simplicity let's assume that the wind gradiant changes the wind direction significantly, from a 15 knot left X/W to a 15 knot right X/W, without changing the headwind component by much. What will happen is that the nose of the aircraft will weathervane in the new relative wind, from being offset to the right of the ground track, to being offset to the left of the ground track. Conservation of Momentum dictates that the ground track will not change.

The new, modified, "Wind" will NOT "Push" the aircraft onto a new ground track. This is because the "Wind" is not a real thing. It is just a abstract measure of the difference in velocity of two different reference frames. Once off the ground, in the air, "Wind" does not exist (except transiently, from wind shear). The only wind an aircraft feels is relative wind caused by motion through the airmass. and that (ball centered), is from straight ahead of the nose. Ball centered, and flying coordinated (without a boot full of rudder), there is no wind force pushing on the side of the aircraft.

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Traffic collision avoidance system (TCAS) protected volume calculation
I am attempting to determine the TCAS-protected volume by utilizing the tau values listed in the TCAS table

(Reference: Page 23 FAA TCAS-II guilines)
The TCAS table provides distinct tau values for the Traffic advisory (TA) and resolution advisory (RA) zones. Based on these values, one would expect the protected volume to take the shape of a circle when viewed from the top. However, upon further examination of figures provided by the FAA FAA-TCAS-II or on Wikipedia, it appears that the TA and RA zones are actually represented as ellipses.

Wikipdia TCAS
Can anyone provide insight on the reason for the TA and RA zones being represented as ellipses instead of circles and the methodology used to determine these ellipses?
Edit: Based on the discourse in the comments section, it has been determined that the zones in question should adopt an elongated shape oriented in the direction of heading, as opposed to a circular shape. Despite this conclusion, the issue of determining the precise shape remains unresolved. It is imperative to consider multiple parameters in order to accurately determine the shape, and the utilization of specific methods or equations may prove beneficial in this regard.

Perhaps they are ellipses because if two airplanes are on track to collide, one or both will enter the end of the others' ellipse before it would enter a sphere?

@Someone, But in some figures, those two aircrafts are not aligned on the major axis of the ellipse. [link] (https://tinyurl.com/ep4bu4hw)

I think my explanation still applies to that diagram? A plane behind you isn't as much of a problem as one in front of you, right?

@Someone, Thank you, that makes sense. If my understanding is correct, the TA and RA volumes are determined solely by the characteristics of the interrogated aircraft and are not affected by the presence or characteristics of any intruding aircraft. Additionally, it is my understanding that these volumes should take the form of an elongated shape, such as an ellipse when viewed from above, as collisions are more likely to occur in the aircraft's heading direction. My question is, what methods or equations can be used to determine the locus of that shape?

Figure 14 suggests that the shape is not an ellipse.

The reason they take such a shape is that the range tau calculations is based off of closing speed, as defined on page 23. This means that the TCAS protection volume with respect to an aircraft directly ahead should not include anything aft of the subject aircraft.
The locus of the projection of this shape onto a 2d plane can be found by calculating the range tau for a given target and comparing to Table 2.

Agreed, it may not be an ellipse. Can you please elaborate more on how to calculate the locus ? Thank you,


text:
How to calculate optimal flight climb angle?
I am trying to calculate the optimal flight climb angle based off of some basic power calculations for an aircraft on steady climb with an angle of theta. Doing a balance of forces I obtained the thrust force, then multiplied by velocity to obtain power. The power was time independent, thus multiplying the term for power by time I obtained the energy, and then I try to optimize this by trying to find an angle for which energy is minimized, however it seems only pi/2 radians (90 degrees) gives a minimum on the graph of energy consumption which I obtained. Did I do something wrong? Is my approach wrong or is the question in itself flawed?
I attach my calculations below as images, thank you!

PS: This is not for homework, this is an interest of mine, I am on my second year studying aerospace engineering and am doing this (studying the efficiency/power equations of a UAV) as a way of getting 'ahead of the curve'. Any feedback on my method is appreciated :)

Without having read the whole derivation, do you realise that there is typically value in travelling horizontally during the climb. You usually want to minimise your energy consumption over the whole flight. If you climb straight up (e.g. by exchanging speed for height) you spent least energy during the climb phase, but you didn't get any closer to your destination and so you consume extra energy for the longer cruise flight segment.

And I think you'd better ask to merge the two profiles

I know is possible to merge two profiles but I don't remember how... I suppose the question is correct here but I think it would be more efficient if you post the whole idea of your project in one single place instead of spreading it among several posts, only my thought

I accidentally created two accounts; how do I merge them?

please DO NOT post important content only as images. it is very unwelcoming to people using screenreaders and prevents them from participating. you can use mathjax here to format the equation properly

The optimal flight rate of climb angle can be derived from Vy.
Basically, at Vy, one flys the plane at optimal angle of attack and optimal thrust output.
As we have learned, lift is less than weight in a climb.  Lift requirement is cosine climb angle × weight.  The "excess power" can be used to climb, with optimal Angle of Attack providing the least induced drag.
Practically, optimal angle of climb can be tested by measuring rate of climb per unit time at various climb speeds (angles at full throttle).  This testing should also yield Vx, the best angle of climb per horizontal distance covered to safely clear an obstacle.
Another option worth considering, if there are no altitude restrictions, terrain, or obstacles, is cruise climb, which can yield slightly faster arrival time to destination.

Ah I see, so I look for an optimal v*sin(theta) not an optimal theta, thanks!

Did I do something wrong?

No, if you have no thrust limitation, your result of a vertical climb is correct. Rockets ascend that way initially while air is dense to minimize the energy expended.
On the other hand, the formulas you copied into your question assume a shallow climb since they apply small angle approximations. Also, thrust is not explicitly expressed as a function of speed and the acceleration needed to stay at the same IAS during climb is also neglected.
To answer more precisely, it would help to know what aspect of the climb needs to be optimized. Generally, you should express the force equilibrium in a climb as precisely as possible and then derive the equation according to the quantity to be optimized. Where the derivation becomes zero you will find the optimum.

I may have missed something but your drag equation seems naive and so gives the wrong sort of speed-drag curve. You need to include the induced drag component.
Vx is CAS for best angle of climb[minimum distance], Vy is CAS for best rate of climb[minimum time] Both are for specific aircraft configurations, changing something like wing area, engine power, or the shape of the propeller will change both the speeds and the resulting angle and rate.

The easiest way to get the speed for best rate of climb is to write down its equation first and then make the substitutions/simplifications.

Being $\gamma$ the climb angle, the (simplified) equilibrium equations on the horizontal and on the vertical direction are:

$T=D+W\sin\gamma$
$L=W\cos\gamma$

with the vertical velocity aka rate of climb defined as:

$V_v=V\sin\gamma$

Under the hypothesis of small climb angle (less than some 15°), $\cos\gamma$ is practically 1. Getting $\sin\gamma$ from the first equation and $W$ from the second one and substituting them in the third equation, one gets:

$\gamma=\arcsin(\frac{T}{W} - \frac{1}{L/D})$
$V_v=V(\frac{T}{W}-\frac{1}{L/D})$

Now we can substitute in the latter the relevant expression for lift and drag and then equate to zero $\frac{\partial V_v}{\partial V}$ in order to get the best rate of climb.
Since you have a constant thrust, the derivation of $V_v$ gives:
$\frac{\partial V_v}{\partial V}=0=\frac{T}{W}-\frac{3\rho V^2C{_{D_0}}}{2W/S}+\frac{2KW}{\rho V^2S} \Rightarrow V@\text{max} V_v$

As usual for the usual impolite downvoter: "Please consider adding a comment if you think this post can be improved" And: "Downvote answers that are incorrect or don't provide sufficient information" –


text:
What does "speed checked" mean?
Here is a Scenario:

PF: Flaps one.
PM: Speed Checked, Flaps one.

What does that mean and why do they have to say "speed checked" every time?

Where did you get this landing scenario from?

@Mast literally any cockpit video of a final approach and landing on YouTube will contain that.

Because there is a maximum deployment speed for things like flaps, gear extension (and sometimes retraction). Exceeding these speeds and using those devices can cause damage to control surfaces or other equipment. The speed check is there so that when the PF calls for flaps, the PM remembers to check the speed before performing the action.

Also note that the air speed indicator has a white arc marked on it showing the range of airspeeds for which flap deployment is safe.

@PaulMitchell Or two horizontal, orange bars (for Airbus)

If you try to extend the flaps while travelling at excessive speed, it won't damage the flaps - they'll simply refuse to extend until you slow down.

@Sean that might be true for Airbus designs (?), but not universally.

Both maximum and minimum speed. If the flaps were 2 before, you check that you are fast enough that you don't risk stalling if you retract flaps and if they were 0 before, you check that you are slow enough that they won't be damaged.

@PaulMitchell, aircraft that have “flaps one” and two crew so that the calls are made don't have a white arc. They have marks annotated with ‘F’ on the speed tape that move around depending on current conditions.

Some companies mandate that the PM verbalise "Speed checked", but it's utterly useless verbiage.
Firstly, the PF should already have checked the speed before asking for the next flap setting.
Secondly, pilots have a history of simply saying "Speed checked", but not actually checking anything. All part of the ritual of PF says Flaps x, I say "Speed checked" and move the Flap Lever.

Whoever changing flaps is also responsible for speed checking we can debate on if it's good or bad but that's the protocol, Of course PF would know the right speed to change flap and would have that in mind, but the responsibility is still on PM's shoulders.

"Secondly, pilots have a history of simply saying "Speed checked", but not actually checking anything." That's usually referred to in the accident report as "complacency". Good pilots will actually perform the check.


text:
Is the Airbus approach more friendly (in case of incapacitated pilots) in terms of a passenger being able to fly the plane?
Is the Airbus approach technology more friendly to a new pilot or passenger than a Boeing haptic approach?

Is this a filosofical question?

No , just  witch  one of this two  a/c is friendly user   for non pilot's .

Spelling errors aside, your question doesn't make sense.  Are you asking if it is easier for an opportunistic new pilot to transfer into Boeing or Airbus, or which one would be easier to fly by a passenger if the pilot was incapacitated?

I just googled the word "heptic" and uhhh... is that what you really meant?

:))),no. Tactile feedback from the control's.

Haptic feedback's is what I meant to say.

Possible duplicate of Can a passenger realistically replace suddenly incapacitated pilots?

If they have to pilot it manually, without training or guidance, a passenger has about as much chance to land an airliner as the airliner has to just happen to land on its own as it runs out of fuel. At least there will be less of it to burn.
It's not a ground vehicle, you can't wing it, and the runway is tiny compared to the sky.
Talkdown landings are a thing in GA and in a modern airliner it would come down to setting up the autoland system. However, the talkdown landing would be performed by the cabin crew, not a passenger. Cabin crew is trained in basic operation of the radios for emergencies including this one.


text:
If Boeing used two sensors instead of one simultaneously, wouldn’t they be in the same position today?
this article states  that the original version of MCAS was suppose to rely on two sensors,

One sensor will detect a high angle of attack, therefore activating MCAS
The other sensor will detect a high G force and therefore activate MCAS.

But what I don’t understand, is why people use this as an argument against Boeing, as if they should have went with that idea? If the high g force sensor was faulty, wouldn’t it technically need a second sensor looking at a high g force, in order to compare the two?
So basically if they had stuck with that idea, we’d still be here today?

The combined “2 input” AOA and G load design was only used in testing and never used in the production aircraft.
The final MCAS design uses only 1 of 2 AOA indications available. The system automatically switches from the left to the right AOA for each flight.

No, the Seattle Times article says "two factors," not "two sensors." The reporter doesn't know the difference between a parameter and a sensor and thinks that the two parameters originally used to trigger MCAS (AOA and g-loading) were replaced by one AoA sensor, when in fact the new triggering parameters were: AOA, Flaps retracted, Autopilot off. The system used one AOA sensor per FCC before, and STILL used one per FCC when the MAX entered service. Just another example of the utter rubbish that the news media put out while doing a crash investigation although utterly incompetent in aviation.

The problem is that there is no redundancy in the sensor input. The quote from the article is:

This original version of MCAS, according to two people familiar with the details, was activated only if two distinct sensors indicated such an extreme maneuver: a high angle of attack and a high G-force.

So on the original design, MCAS activation required two sensors detecting an input over a certain threshold, and in itself this creates protection against false positives.
There are two major failure modes for sub-systems:

Zero output, where the sub-system simply stops outputting a signal.
Hard-Over failure, where the sub-system outputs a false positive. This is what happened with the AoA sensor in the two MCAS disasters.

With the original design, if one sensor would go hard-over, MCAS would not activate and the system would be protected against a single failure. But in the certified config, the activating input was not checked against any signal and MCAS repeatedly activated.
Further notes on the AoA sensors, from the final accident report page 45:

There are two AoA indicators on the B737Max, and only one was used for MCAS input.
There was an AOA disagree detection installed - as an option which Lion Air had not selected at the time of the accident:

Accordingly, the software activated the AOA DISAGREE alert only if an airline opted for the AOA indicator. At the time of the accident, Boeing advised that the AOA indicator has been selected by approximately 20% of airlines.
When the discrepancy between the AOA display requirements and the software was identified, Boeing determined that the absence of the AOA DISAGREE alert did not adversely impact aircraft safety or operation. Accordingly, Boeing concluded that the existing functionality was acceptable until the originally intended functionality could be implemented in a display system software upgrade, scheduled for the third quarter of 2020.
Lion Air did not select the optional AOA indicator feature on the PFD of their 737- 8 (MAX) aircraft. As a result, the AOA DISAGREE did not appear on PK-LQP aircraft, even though the necessary conditions were met.

The safety analysis of the certified system has proven to be fatally incorrect, and this is what is so baffling. A single mode of failure was allowed to activate a flight critical system, by the most experienced aerospace company on earth. Plus: the incorrect safety analysis was accepted by the aviation authority whose function it is to protect us, the passengers.

I think you can also add that Boeing and the FAA also decided that the pilots didn't need to be trained on this system.

But even if they use one sensor, how can it not reject just based off the sensors differing? I know they work simultaneously, but couldn’t they have been an easy change?

@Firefighter1 Very, very good point!

The answer is seriously flawed. One  of the conditions that must be satisfied for the system to activate cannot serve as "protection against false positives" of the other condition because the parameters are independent and unrelated, and completely unaware as to the validity of each other. The author of the article had no understanding of basic engineering yet attempted to conduct an accident investigation and perform engineering analysis. Also, the parameters are used as analog variables that trigger MCAS and modulate its duty cycle, not as binary discretes that merely flip MCAS on or off.

@Robin Bennett "Boeing and the FAA also decided that the pilots didn't need to be trained on this system." Actually, Boeing and the FAA decided that there was no training for this system, i.e. no training was possible. That is why the airplane has returned to service and there is STILL no flight simulator training for MCAS. But since you think there should be—btw, you're not the only one to think so—please enlighten us with some details on what that training should consist of.

@PeteP. I'd have thought that was obvious. Pilots should know that the system is there, that's it's vulnerable to a failure of the AoA sensor, how to recognise a failure and how to disable the system and regain control.

@Robin Bennett  The pilots can't detect normal MCAS operation, can't control/adjust it, can't turn it ON or OFF, there is no mention of it in system fault messages, checklists or procedures. Nonnormal operation manifests as a runaway stabilizer trim, which has multiple causes and is handled without fault isolation, by the same NNC regardless of cause, and for which initial and recurrent simulator training is standard.
The system is transparent to the flight crew, so no MCAS-specific flight-sim training is necessary or even possible and there is no need for its inclusion in the FCOM.

@PeteP. Evidently, there was a need for including the existence of MCAS in the FCOM. It caused a repeating stab trim runaway, and trim did not run away all the way.

@Koyovis The Runaway Stab Trim NNC was already in the FCOM and none of the possible causes were listed. The definition of RST: The stab moves—un-commanded—to a position it should not be. About 2–3 seconds into a RST the pilot will notice the pitch attitude deviating and will instinctively restore it using the elevator. At 4–5 seconds s/he senses that the elevator force needed to maintain pitch attitude is abnormally high and getting worse. By 6–8 seconds s/he is reaching for the electric trim to assist with the elevator force and notices that the stab is being trimmed—excessively…

…There is no use for discerning whether the runaway is intermittent or continuous or what is causing it. Not only is the system not designed for quick and more in-depth fault isolation by the pilots beyond "autopilot" and "other", but the recovery procedure doesn't care; regardless of cause it is essentially: shut down autopilot… if that doesn't do it, shut down electric trim…

The question to all those experts who insisted that the pilot needs to know if the runaway is continuous or intermittent… How would you determine that? By watching and waiting— i.e. doing absolutely nothing while the nose slews towards Heaven and a stall, or towards Hades and your ad hoc gravesite—until the stabilizer either reaches the physical travel limit or stops short of it?! And then, for what do you use that little nugget of information? (while your fellow pilot stares at you with growing alarm, unsure whether you are paralyzed by shock, or you are suicidal).

It is mind-boggling that all the experts who declared that the pilots were lacking training for the new and unexpected type of runaway because Boeing "hid" the system, never bothered to run through the scenario in their head to validate it… and discover its absurdity.

@PeteP. There is validity in your argument. However, the pilots  of the 2 crashed planes were trained for stab runaway, and did not recognise the MCAS behaviour as such. So something in the MCAS behaviour did not match their simulator training.

That's a completely incorrect understanding of the article. The summary should be:

MCAS activates if:
  a) Sensor detects a high angle of attack
  and
  b) Sensor detects a high normal G load

If one sensor is erroneous and and the other one isn't, then MCAS would not erroneously activate.

And what happens if the high g force sensor is faulty and not reading correctly, but the plane is experiencing a high g force and high angle of attack?

@Firefighter1 Then MCAS would not kick in. You may encounter a stick force reversal and a pitch up as a result. You will still have the stick shaker activated in this flight regime.

Actually, the article itself is nonsensical. The author lacks basic competence in engineering and has confused the various conditions that must be satisfied for the system to activate as being "multiple points of failure," not realizing that they are independent and unrelated parameters. He also doesn't realize that the modified system required Flaps_Up and Autopilot_Off in addition to AOA_High in order to trigger MCAS, which blows his "single point of failure" conspiracy to bits.

@JZYL True, MCAS would not kick in, but there would not be any stick force reversal, that is not a characteristic of the airplane. There would also not be any pitch up, whether due to stick forces or anything else (other than pilot induced); that is also not a characteristic of the airplane. And whether the stick shaker goes off or not depends solely on the angle of attack: if it is high enough to trigger the stall warning, it will activate; doesn't have anything to do with MCAS. For clarity—MCAS is NOT an anti-stall system or stall-recovery system, regardless of what a news reporter says.

@PeteP. I never claimed MCAS was originally designed for anti-stall. As far as I understand based on publicly available sources, it's required for certification and adhere to the requirements Part 25 related to stall characteristics and maneuver stability.

@JZYL Understood, it was the reporter who mischaracterized the system.
Although you correctly stated AOA and G-load sensor values as the conditions a) and b) that must both be satisfied for MCAS activation, your next sentence impugns the first by implying that activation depends on the validity of those sensor values! How does the system know if a sensor value is erroneous or valid?
Whether MCAS activates or not simply depends on whether the sensor values are in the range to satisfy conditions a) and b) or not, regardless of their validity.


text:
Does the Ground Proximity Warning System (GPWS) see through clouds?
Or can it only detect terrain on a clear day or night? I’m mostly asking because of PIA268
I know GPWS is much more reliable in todays  time, and I’m unsure if the accident flight even had a GPWS system, but is it safe to say the chances of that scenario repeating, are minimal? Assuming the system is functioning properly and or the crew reacts properly to the warning.

Most aircraft nowadays have the Enhanced GPWS where aircraft GPS position is matched against a worldwide terrain and obstacle database, so that terrain and obstacle warnings can be generated without the need for a ground radar. Just a comment, as it’s relevant but doesn’t answer the question.

Modern airliners typically use a Terrain Awareness and Warning System (TAWS) with two sources of information for triggering warnings: the radio altimeter and a global terrain database. See e.g. the Boeing 737 NG, which uses EGPWS (Enhanced Ground Proximity Warning System):

Ground Proximity Alerts
The GPWS provides alerts for potentially hazardous flight conditions involving
  imminent impact with the ground.
The GPWS monitors terrain proximity using an internal world wide terrain data
  base. Proximate terrain data shows on the navigation display. If there is a potential
  terrain conflict, alerts are provided based on estimated time to impact. These alerts
  are “look-ahead terrain alerts.”
The GPWS provides alerts based on radio altitude and combinations of barometric
  altitude, airspeed, glide slope deviation, and airplane configuration. The alerts are
  for:

excessive descent rate
excessive terrain closure rate
altitude loss after takeoff or go-around
unsafe terrain clearance when not in the landing configuration
excessive deviation below an ILS glide slope
excessive deviation below glidepath

These alerts are “radio altitude based alerts.”

(Boeing 737 NG FCOM 15.20.11 Warning Systems - System Description, emphasis mine)
For the terrain database to work, the aircraft needs to know its position from a GNSS source (like GPS), but can also use another source (like inertial position) as backup:

5.3 Primary Horizontal Position Sources. Horizontal position for TAWS must come from a GNSS source
  meeting ETSO-C129a or any revision of ETSO-C145, ETSO-C146, or ETSO-C196 (or subsequent). As an exception, TAWS equipment limited to installation in aircraft where the EU Regulation on Air Operations
  does not require such equipment may be configurable to operate solely on a non-GNSS position source.
5.4 Alternate Horizontal Position Sources. Retaining TAWS functionality during GNSS outage or
  unavailability provides a safety benefit. It is acceptable and recommended to incorporate a secondary, non
  GNSS position source, to provide horizontal position when the GNSS is not available or reliable.

(ETSO-C151c, thanks to DeltaLima for pointing this out)
So there are two signals that need to work in clouds for full TAWS capabilities.

Radio Altimeter:
For the radio altimeter to work in a cloud, the radar signal needs to be able to penetrate the cloud and reflect off the ground. Only the part of the cloud below the aircraft is relevant here. Airbus published a nice overview of factors that could result in erroneous RA values:

The external causes may be linked
  to aircraft flying over:

Other aircraft, hail clouds or
  bright spots, i.e. terrain presenting
  reflectivity variations.
Runways contaminated with water or snow.

In these cases, the RA condition
  may not be detected by the systems,
  which continue to use the erroneous
  RA values.

(Airbus Safety First Magazine - Radio Altimeter erroneous values, emphasis mine)
So normal clouds should not affect the radio altimeter, but clouds with dense precipitation (like hail) can have such an affect. Note however, that if the radio signal reflects off the cloud itself, it could result in a false positive alert, but not a false negative.
GPS signal:
Here, the clouds above the aircraft are relevant, since they could block the signal to the satellite. The GPS signal is however largely unaffected by weather:

Does RAIN or SNOW or CLOUDS affect the reception of my GPS receiver?
Answer:  No.  Not so as the user can tell without instrumentation.
[...]
The GPS signal frequency of about 1575mhz was chosen expressly because it is a "window" in the weather as far as signal propagation is concerned.

(gpsinformation.net)
Even if the GPS signal is temporarily lost, the Alternate Horizontal Position Source can take over. The inertial position accuracy from the ADIRU would slowly degrade over time, but provide a good position estimate just after the GPS signal is lost.

This is a good basis for an answer, but you are missing GPS as sensor. Without knowing the position, the terrain database is useless. GPS is not affected much by clouds.

inertial systems are not accurate enough for EGPWS, by far. ETSO151c on TAWS (generic name for (E)GPWS) says in section 5.: Horizontal position for TAWS must come from a GNSS source

@DeltaLima That's interesting, I though it would just use ADIRU position. I updated the answer...

And I upvoted it :-)

"Answer: No. Not so as the user can tell without instrumentation." eh... I'm not so sure. I use a Garmin running watch and it can take a full minute to get a GPS lock on a cloudy day, while it only takes seconds on a sunny day. This is under the same conditions, otherwise - I walk the same direction out of the same building 5 days a week into a parking lot and keep walking in a straight line until I've got signal (or have to deviate because I'll cross a street).

@FreeMan I assume an aircraft GPS antenna is somewhat bigger and more sensitive than the one in your watch.

@Bianfable I sure hope so!!


text:
What were other possible solutions proposed to solve the problem of clean weapons separation for the F-18 Super Hornet?

I'm curious as to what other solutions were considered besides canting the pylons.

How was it handled by other clean-slate designs subsequent to the F-18?

At least in the helicopter world weapons are canted to minimise drag at cruising speed. There's a quite wide range of speeds and attitudes where weapons can be safely jettisoned. It should be the same for airplane too.

welcome to aviation.se. I'm sorry, but as currently is phrased, this question is fundamentally asking for opinions. if you can reformulate it such that it can be answered in a factual manner, I'll be more than happy to reopen.

"I know that..." - Documentation on this please? On all the pics I see, the wing pylons are vertical.


text:
Is induced drag zero for finite wing with constant lift distribution (dΓ/dy=0)?
Part 1
Observing how induced drag is derived, induced drag is loss of kinetic energy due to total vorticity that is produced by wing.
I want to find induced drag of finite wing with L=const over span.
Finite wing with constant lift distribution is just math concept,not existing in reality, cant be tested in any experiment because even wing has lots of twist,the wingtip area cannot satisfy Γ=const, too much pressure leaking.
This is formula for local induced angle of attack, if L=const over span, circulation Γ=const, dΓ/dy=0, implies alpha= 0 thus Dind.=0
-I am intersted will in Treffz plane get same result, has equation "dΓ/dy" inside?-

Part 2
By definition airfoil has zero induced drag, I want to check this mathematically.
Airfoil is infinite wing with L=const over span, I think this  integral (picture below) for alpha induced is valid. Same like in part 1 if dΓ/dy=0, Dind=0.
But when I use this formula: Di= L* 2 / (0.5 x ρ x π x V* 2 x b* 2) and put infinity instead b and L,
(infinity wingspan will give infinity lift), I get Di=∞/∞
If I use  L'Hospital's rule will I get Dind=0?
For specific case where L=W, indeed this formula get Dind=0, but I want to analyze in general case.

Even if lift distribution were constant spanwise, lift would go anyway to zero at the end of the wing because... well, there's no wing anymore and there you would have a huge variation of lift i.e. huge generation of induced drag. Actually this sudden variation of lift would be so big to produce a much bigger induced drag in respect to a smoother (ideally elliptical) spanwise lift distribution.

Mathematically, the integral for the induced drag (or induced speed or induced angle) is extended from $-\infty$ to $+\infty$, but since the integrand is zero outside the wing, then the integration is normally written between $±b$. Anyway the integration (which is not a normal integration but a Cauchy principal value integration) is done approaching the wing's tips from $\infty$ and therefore what happen just outside the tip does matter. In particular, just outside the wing it must be $\Gamma=0$ because there there's no wing and lift is null.
So in order for $\Gamma$ to be:

zero at the tip;
and constant everywhere, i.e. with $\frac{d\Gamma}{dy}=0$

then it must be $\Gamma=0$ everywhere. This is the only lift distribution which is mathematically compatible with 1. and 2.

In the equation for the induced drag, $b$ should be on the denominator side:
$D_i = \frac{L²}{q \pi e b²}$
Therefore if $b\rightarrow \infty$ then $D_i \rightarrow 0$.
The value of $L$ has nothing to do with this result because for an infinite wing (aka airfoil) the whole maths for the induced drag just doesn't exist in the first place: the integration of the pressure in the drag's direction is just zero for an airfoil and therefore there's no need to elaborate any theory for it. So, when we deal with the induced drag theory, the wing cannot be infinite by mathematical definition and therefore neither the lift.

Wings with (almost) constant spanwise lift distribution can actually be built playing with the chord distribution and/or the twist. NASA played with the twist in the past and got a quite constant spanwise lift distribution:

At the end of the wing, lift is constant not zero. This just mathematical concept, 100% abstract, just like airfoil. Integration shows whenever you have dΓ/dy=0, induced drag become zero.  Yes b is on the denominator side, but infinity wingspan will produce infinity lift, if you don't introduce a specific condition L=W.

"Wings with (almost) constant spanwise lift distribution can actually be built playing with the chord distribution" Key word is almost, this wing has no dΓ/dy=0, especially at the wingtip area. Formula dont know what is one mm out of wingtip, dont take this in consideration.

I updated my answer, let me know if it's clear.

"these are the only two mathematically valid solution of the problem." You mean  integral is not undefined or indeterminate expressions?

I mean that the only possibility for 1) $\Gamma$ @ tip to be zero and 2) $\frac{d\Gamma}{dy}$ to be zero, is that $\Gamma$ must be zero everywhere. Just basic mathematics, nothing to do with induced drag or whatever. If a variable is zero somewhere and its derivative is zero too, then this variable can only be zero. Think about the definition of derivative: the variation of a quantity. If this variation is zero then the quantity doesn't change and if this quantity is zero somewhere then it must be zero everywhere, by definition of null derivative.


text:
How do weapon pylons attach to a fighter's wings?
How do weapon pylons attach to a fighter's wings? I'm particularly interested in the inner structure.

I'd imagine it varies from aircraft to aircraft to some extent.

The pylons are not just for weapons; the term used for the Typhoon aircraft is the Wing Pylon Station Unit (WPSU) and some of those are designed to be able to carry external fuel tanks.
Some aircraft (such as the vernerable F-4 Phantom II) had 4 wing pylons which were more or less permanently attached (unless they were defective in which case they could be replaced); certainly in the years I worked on them I never saw an aircraft without all 4 pylons.
Other aircraft (such as the Typhoon) have pylons that are not necessarily all fitted
(there are locations for up to 8 wing pylons)
Here is a fit using only 6 of the pylons and all 5 fuselage hard points:

Here is a different setup using all 8 wing pylons:

Source
The attachment is relatively simple (it has to be as it can be a hangar operation for operational fit); the pylons are physically attached with mechanical mounting and electrical connectivity (to actually operate the items being carried); the pylons that can take external tanks also have fuel feed points.
The pylons also have communication links for the aircradt to 'talk' the whatever happens to be fitted on the pylons (the data could be commands, video feed, sensor data, stores readiness - whatever is required for a particular type of store on the pylon)
It is important to note that the all the hard points are considered safety critical as you do not want to fire / jettison something when not commanded and you do want that at the appropriate time.
The inner structure of the pylons is almost completely full (very little space unused) which keeps the unit as small as possible (which enhances its ability to withstand aerodynamic forces) and as light as possible.
The electronics within the pylons are somewhat expensive as the internal temperature can be as low as -50C or lower at high altitudes; the leading edge is a low drag surface to minimise heating by air friction.
Different pylons will have slightly different attachment methods but they all need to withstand the aerodynamic forces and provide electrical and communication functionality.
Update
Here is a close up of an F35 pylon (designed for air to air weapons):

Source
The mounting bolt position is clearly shown (there is another on the other side of the pylon). The pylon fits into an acceptor slot and all the various connections are made simply by placing the pylon in the correct position and sliding it in. The direction of sliding is from the front so aerodynamic pressure keeps it in position.
Interesting fact. One fine day I was working on the flight line at RNAS Yeovilton when an american F-4 flew over; he was doing a bit of hot-dogging. The aircraft had two external wing mounted Sargent Fletcher fuel tanks and when he did a high G pullup, the tanks separated from the wing pylons and landed on a roundabout in the middle of the road.
This is one of the issues with wing pylons and stores; they impose a g limit on maneuvering or things literally break away.
I understand his boss was not at all pleased.

if you have and could share knowledge about the structure of the pylon attachment points on the wings, it would improve this otherwise comprehensive answer.

I will do that in the morning (my time) :)

Why does it appear that the F35 in the photo has a missile mounted backwards?


text:
Approx 1948 Brasil Brazil Airliner...what is it? Taildragger?

What plane is this? It's a taildragger, 4 blade prop, twin engine plane. The photo was taken approximately in 1948, maybe in Brazil?

"Flota ... cante" was enough to confirm Argentinian FAMA. So not Brazilian, Argentinian. That at least narrows down what it is and when, even if not all the way to a single type.

What is the lump on the top? Satellite internet?

@Harper Are you sure it's not a cocktail shaker?

@Harper It's a streamlined housing for a loop antenna, almost certainly for radio direction finding.

Looks like the prop rotates the  "wrong" way.  ( ccw as viewed from behind )

@quiet flyer nice observation!

Maybe not uncommon for non-US aircraft?  But it did catch my eye.

The airliner in the picture is a Vickers VC.1 Viking, registration LV-AFI, of the former Argentinian operator Flota Aérea Mercante Argentina.
According to this source, the plane served the
Secretaría de Aeronáutica under registration LV-XFJ for less than a month, from 10.9.1947 till 4.10.1947 before transferring to FAMA.
After FAMA, the plane in question served Fuerza Aérea Argentina from 4.5.1949 till 11.11.1951 under registrations T-80 and T-50.
Wikipedia: Vickers VC.1 Viking
Wikipedia: Flota Aérea Mercante Argentina (in Spanish)

How did you determine the registration number from this photograph?

@Jacob Krall under the wing, between the guy in all-whites and the one with white shirt and dark pants, you can see FI. To left of that, between two guys dressed in white, you can see the sharp bottom of a V. LV-AFI is the only VC.1 in FAMA fleet with a reg ending in FI. Registrations of Argentinian VC.1's were painted on the exact location shown in the picture, so there's pretty much zero chance of making a mistake.


text:
What does Lion Air faking the repair of the AoA vane mean for the Florida repair shop that ceased operations?
This is a lengthy read, but worth it. I'll quote the main piece I am speaking of.

At the Bali airport, a vane, known as an angle of attack sensor, was replaced. Crash investigators were presented with photographs supposedly showing that a mandatory test was done after the vane had been replaced. But upon further inspection, investigators concluded the photos were from a different aircraft. “This is a test that Lion Air was required to do, and they didn’t,” said John Cox, an aviation safety consultant. If the test had been done, engineers likely would have realized the vane was calibrated incorrectly by 21 degrees

Source: nytimes.com
On Friday, October 25th, 2019, the FAA revoked the repair station certificate of the Florida repair shop that had sold the second-hand part to Lion Air.

The FAA revocation order said Xtra “recklessly and systemically” failed to comply with federal safety requirements.

Source: Seattle Times
Would the finding in the first article imply the Florida repair shop can reopen for business? Or, did they sell Lion Air the AoA and was miscalibrated by them, and therefore the business will remain closed?

AoA = angle-of-attack

The FAA action, while supposedly not directly related Lion Air but more to Xtra's problems with working on parts they were not authorized to work on because they hadn't demonstrated that had everything in place, is obviously politically related to the event because the crash put the spotlight on Xtra and the FAA had to do something once having lifted that particular rock.
So from a strictly legal standpoint, Lion Air's maintenance actions don't help Xtra and what will happen is Xtra will have to make reforms and then go back to the FAA to try to get their repair cert reinstated independently of any Lion Air actions.
Normally what happens is a part goes to a repair facility, and the repair shop puts it though an Acceptance Test Procedure (ATP) as per the manufacturer's Component Maintenance Manual (CMM). There is usually some kind of test rig that has to be made (instructions for making it in the CMM), that runs the specified functional tests on both ingoing and outgoing parts.
So the part goes in, and gets an incoming ATP. If it passes the incoming ATP, it's considered serviceable and gets tagged NFF (No Fault Found) and sent back to the airline as serviceable.  If it fails ATP, it gets broken down and repaired as required.  It then gets an outgoing ATP (the same test normally) to validate function before it is tagged repaired/serviceable.
I can't really tell from the article if the mis-calibration was inherent to the vane as received or was something screwed up when the airline installed it.  Notwithstanding the likelihood that Xtra was turning parts around that they don't appear to be approved to repair, it's not uncommon for parts to come back to an airline NFF, or repaired, and still fail when it's installed on the plane.
So either Xtra had the proper manual, test rig, parts and tools, training etc. for fixing these vanes or they didn't.  The FAA's action makes it sound like they didn't and were maybe just receiving units and doing some other test they made up themselves, or maybe just smiled at it and sent it back out. Hard to say.
In any case, receiving a part back with a serviceable tag is no ironclad guarantee that it will work in service, and "bad from spares stock" happens from time to time.  No system is perfect.  The business depends to some degree on the redundancy of having two and three of everything to cater to random failures no matter the background causes, except in this instance Boeing decided to let that single-point-of-failure spot in the system architecture get through cert, and here we are.

As part of the investigation the authorities followed that part through the system and scrutinized every step of the AoA's life. When they looked at Xtra they found numerous issues with the company and how they handled repairs. The FAA's press release on Xtra says:

According to the order, Xtra failed to comply with requirements to
  repair only aircraft parts on its list of parts acceptable to the FAA
  that it was capable of repairing. The company also failed to comply
  with procedures in its repair station manual for implementing a
  capability list in accordance with the Federal Aviation Regulations.
  Xtra is a repair station certificated under part 145 of the Federal
  Aviation Regulations.

Translation: they didn't stick to what they were allowed to fix, they weren't supposed to try to fix the AoA sensor. Next:

The FAA began its investigation in November 2018. Investigators looked
  specifically at the company’s compliance with regulatory requirements
  that apply to its capability list, and records and work orders for
  aircraft parts it approved for return to service. The investigation
  determined that from November 2009 until May 2019, Xtra failed to
  complete and retain records in accordance with procedures in its
  repair station manual to support parts on its capability list. The
  company also did not substantiate that it had adequate facilities,
  tools, test equipment, technical publications, and trained and
  qualified employees to repair parts on its capability list.

Translation: For a decade Xtra can't say for sure what they fixed or how they fixed it, and couldn't show they had the tools or the talent to fix anything they were allowed to.
So Xtra have a serious systemic problem, almost every single part they have ever touched is now suspect, so they've been shut down. I don't know whether the repair to the AoA was faked or simply botched with bad records, but either way I wouldn't want to fly in an airplane which had safety critical parts from Xtra.


text:
Why is cold temperature correction not applied from FAF to MAPt on RNP approaches using LNAV/VNAV minima?
Cold temperature corrections are made to altitudes in the Flight Management Computer (FMC) because, at low temperatures, the altimeter shows a higher altitude than the aircraft's true altitude. For instance, at -10°C, if the aircraft is at 3,000 ft according to the altimeter, the true altitude might actually be 2,800 ft due to the cold temperature causing an underreading of 200 ft.
At the company I fly for (B737s NGs and Max), we apply temperature corrections to altitudes on the approach and missed approach profile for any altitudes below the corrected Minimum Safe Altitude (MSA).
However, company procedures I fly for specify that when flying an RNP approach and using LNAV/VNAV minima, we should not apply temperature corrections to altitudes between the Final Approach Fix (FAF) and the Missed Approach Point (MAPt), though we are required to correct the Decision Altitude (DA). If we are flying the approach using only LNAV minima, then the Minimum Descent Altitude (MDA) is temperature corrected, with an additional 40 ft added. Moreover, when only LNAV minima is used, all altitudes below the MSA are temperature corrected.
What is the rationale behind this? Why would it be inappropriate to apply temperature corrections between the FAF and MAPt when using LNAV/VNAV minima (a 3D approach)? What is different about an approach that uses only LNAV minima (a 2D approach)?

My question differs from the existing ones as it focuses on why cold temperature corrections aren’t applied from the FAF to MAPt when using LNAV/VNAV minima and how this differs from LNAV minima procedures.
We do not currently operate RNP AR (Authorisation Required) approaches or those using LPV (Localiser Performance with Vertical Guidance).

They are not applied because the allowed temperature range is included in procedure design. That means the Final Approach Segment (FAS) is protected down to what is called the Promulgated Minimum Temperature. The lowest allowable OAT reads somewhere in the notes as "Baro-VNAV N/A below -15C" or something similar.
The APV Baro-VNAV allowes for 75 ft deviation below glideslope and this includes temperature corrections down to the promulgated temperature as indicated in the chart. If OAT is below ISA, the actual flight path will be lower and glide angle will be shallower than indicated in the chart but required obstacle clearances will be satisfied.
If FMS compensates for temperature, as described in Bianfable's answer, this temperature limitation does not apply (of course, as described in your company manuals)
The procedure design in different types of RNP approaches is different although they are described on the same chart. While the vertical profile for 2D approach with LNAV minima is similar to other 2D approaches such as VOR, the 3D APV Baro-VNAV does not have any stepdown fixes or MDA. If they are drawn to the chart, they only apply when flying to LNAV minimums.
This is further complicated by the guidance method used. At least in Airbus it is allowed to fly the 2D approach (ie. LNAV minimums) using the same 3D guidance as Baro-VNAV. When doing so, all the stepdown fixes and MDA will apply and must be monitored from the chart by the crew during the approach.

This sounds like you are flying a compensated baro VNAV approach, where the FMC provides compensation for temperature effects automatically and therefore does not require the pilot to correct altitudes manually.

RNAV instrument approach procedures use barometric altitudes and barometric vertical navigation (Baro VNAV) in the approach design. As a result, true altitude can differ greatly when temperatures become extremely hotter or colder than standard. [...]
Honeywell NZ6.1, EPIC, APEX/ACE, and NG FMS all have a temperature compensation (temp comp) capability. This function provides temperature compensated VNAV altitudes during operations in extremely hot or cold temperatures. Temp comp raises the waypoint altitude constraint values in cold weather and lowers the waypoint altitude constraint values in hot weather. The FMS adjusts the altitudes for all the waypoints in the approach and missed approach segments of the flight plan, ensuring the aircraft is at the published true altitudes.

(Honeywell: Inside the FMS)
This function is independent of barometric minima, which need to be adjusted manually:

A separate input is necessary to adjust the DA / MDA, since it is not automatically compensated for temperature.

(Honeywell: Inside the FMS)
On the Boeing 737 NG this feature is available since FMC Update 14 released in September 2019:

U14 features:

[...] VNAV temperature compensation gives the ability to semi-automatically adjust the procedure barometric altitude constraints and glide path angles based on a pilot-entered temperature, so the FMS descent path can account for the effects of temperature. [...]

(b737.org.uk: FMC Update 14)
If installed, there should be TEMP COMP REF page on APPROACH REF page 3 as shown here:

(YouTube: 737 FMC U11 to U14.1)


text:
What causes the "dead band" phenomenon during takeoff on the Boeing 737?
During takeoff, the Boeing 737 encounters a distinctive "dead band" phenomenon after the initial pitch reaches approximately 10 degrees. Essentially, a slight increase in back pressure is necessary around 4-5 seconds into the takeoff procedure or when reaching the 10 degrees pitch to sustain the rotation rate.
While this heightened back pressure demand within the “dead band” is quite noticeable during initial training on the 737, it progressively becomes ingrained and intuitive through experience, etching itself into muscle memory.

Rotate at a rate of 2.0 to 2.5 degrees per second. Beware of a
“dead band”  around 10 degrees, and maintain a constant rate
of rotation towards 15  degrees nose up to a pitch limit of 20
degrees.
Boeing Flight Crew Operations Manual (FCOM) - Takeoff
Procedure

Although the Flight Crew Operations Manual (FCOM) addresses the "dead band" effect during the takeoff procedure, as far as I am aware, it is not mentioned or discussed in the Flight Crew Training Manual (FCTM) or the Airplane Flight Manual (AFM).

Based on my understanding, this "dead band" effect during takeoff is attributed to the combination of downwash off the wings and ground effect phenomena, resulting in diminished elevator effectiveness. Is this explanation accurate?
Furthermore, does this dead band phenomenon occur to the same extent in other Boeing aircraft or similar narrow or wide-body commercial aircraft?

WIth T tails on some airplanes the problem is the opposite; you have to relax a little bit to keep the same pitch rate. In that case it's mostly the T tail moving deeper into the downwash field and the fact that the gear with tail mounted engines is farther aft to keep the thing from tipping back when empty.

To your second question, it affects the 767 as well. To your point, primarily ground effect, it does impact other airframes but I think the 737 got so much press around it due to flight simulators emphasizing the effect relative to what some pilots felt the effect was on real aircraft. Most flight instruction curriculum lists it as tail going into ground effect, but the downwash also effects it. Pilots will tell it's noticeable on the 767 as well.

It is noticeable on the real aircraft too.

It seems you already asked this question two years ago. Related discussion at PPRuNe.

Even from your drawing you can see that the wings are aligned at the same height of the elevators. You have then turbulent flow reaching them, reducing their effectiveness (negative lift in this case). Ground effect will also augment the pressure of the lower part of elevators, which is not what you want in this case (lift should be downwards)

Additionally, since the 737 is not fly-by-wire like "Scarebus" I would expect/imagine stick getting "softer" in that moment, similar to a stall. At least in a glider (from experience) we can feel it easily (we have a big window from start of stall until loss of control, so it allows us to train and use only the rudder to balance the wings at low speeds). Advantage is that you get used to keep the stick centered to avoid increasing the stall playing with the ailerons and still allowing full control of bank with rudder.

A question about dead-band has been posted previously by the OP. That one was about a deadband in response of the flight controls with hydraulic systems OFF, this present question is about a deadband during take-off with flight control hydraulics fully functional.

In systems control and response, a deadband is a region where a change in input does not cause a change in output, like the centre deadband in the figure above. In the takeoff rotation deadband that the FCOM mentions, input is the pitch stick position, and output is the aeroplane Nose Up angle. So in the deadband region, further stick deflection does not result in further Nose Up angle.
And we can see in the pictures in OP why this happens: with the aeroplane on ground, nose up means tail plane very much closer to the ground, causing more lift at the tail plane due to ground effect, like depicted in this answer. So more and more stick input is required to further up the nose, described as a deadband.


text:
What defines the end of a "cross-country flight" for ppl aeronautical experience purposes and for general logbook purposes?
Assume "pilotage" is used for all flights other than circuits around the pattern.
Assume, in the flights that follow, at any point where required, an instructor travels to the departure point and approves the flight.
At what point in the following sequences must the pilot stop logging the accumulating flight time as one single cross-country flight--

For general logbook purposes
For meeting the cross-country aeronautical experience requirements for a private pilot's license under part 61 in the USA? (NOT the "long" cross-country requirement.)
To meet the 200-hour cross-country experience requirement for the ATP rating under part 61?
To meet the 100-hour cross-country experience requirement to act as PIC under part 135?

Please explain your answers.
Let's say a pilot does the following:
Case 1:

a) Takes off
b) Flies to a point 60 miles away, full stop landing
c) Flies back to start, full stop landing
d) Flies to a point 60 miles away, full stop landing.

In case 1, would it change the answer in any way if I revealed that the pilot got out of the airplane and slept overnight between steps b and c only?
How about if she got out of the airplane and slept overnight between steps c and d only?
Case 2:

a) Takes off
b) Lands at a point 60 miles away, full stop landing.
c) Flies to a point 10 more miles away, full stop landing.
d) Gets out of the airplane at eats lunch
e) Flies to a point 10 more miles away, full stop landing.
f) Gets out of the airplane and stretches
g) Makes 10 circuits around the pattern without using pilotage, with full stop landings.
h) Flies to another point 60 miles away, full stop landing.
i) Gets out of the airplane, takes a nap.
j) Gets back in airplane, flies to a point 60 miles away from both the latest takeoff point and the original start point, full stop landing.
k) Rents a motel room and stays over night.
l) Flies on to another place 100 miles away.
m) Stays with a friend for a month, while making 10 short flights around the airport without using pilotage.
n) Flies back to the original starting point.
o) Makes 10 more short flights over the course of the next month without using pilotage.
p) Flies to a point 60 miles away.

In case 2, would it change the answer in any way if I revealed the pilot was on a long vacation and the aircraft and pilot were actually based at the point that the last flight "p" ended up at, and he had departed from there two days previous to the first flight in the list (a)?
Relevant: http://www.boldmethod.com/learn-to-fly/regulations/logging-cross-country-flight-time/

Your question is quite long and you've already linked to an article about logging cross-country time. Can you perhaps make your question more specific? Is there some scenario that isn't addressed in the article you linked? And have you already seen this question?

Related: https://aviation.stackexchange.com/questions/88028/61-133b1-what-counts-as-a-full-cross-country-flight

It is not in the interests of the FAA to provide a specific definition of how long an aircraft can spend on the ground before a flight "ends".
Pilots are expected to use their judgment to deal with weather, fuel planning, air traffic control, etc.  Pilots are also expected to use their judgment when deciding what should and should not be logged as a single cross country flight.
This is good for pilots. The FAA trusts us to do the right thing.
Ok, but what about my questions?

For general logbook purposes you can do anything you want. Exactly nobody cares what's in your logbook except you (and maybe the person interviewing you for a job in your future).

Private, commercial, and ATP experience require hours, not flights. Therefore you may log case 1 as one flight, two flights, or three flights, depending on which is most reasonable in your judgment as a pilot and based on the unique circumstances of the flight.  For the most part this simply means you need to decide whether you want to fill out one, two, or three lines in your logbook.

Similarly, you may log all of case 2 on one enormous line in your logbook, if for some reason the unique circumstances of the flight indicate that that's the best way to do it. (Maybe you're going to the south pole, and the month-long break is because you had mechanical trouble along the way.) Similarly, you may choose to log each leg or even each landing as a separate line in your logbook (for a total of 38 lines), if that makes more sense in your judgment.

The longer the stop, the more difficult is it to argue that it should be considered one flight.  I think it would be exceptionally difficult (though not impossible, see above) to make the case that two hours worth of flying separated by a month of not flying should be considered one flight.

As guidance, remember that your logbook is a reflection of you as a pilot.  If there's uncertainty, ask yourself "How would I like to be perceived, if someone were to audit this logbook?"  If there's still uncertainty, ask an instructor.  If there's still uncertainty, ask an FAA inspector.  They're there to help.

This answer seems to imply that the number of hours logged as cross-country flight time is going to come out the same no matter how we answer my question.  But that is clearly not the case.


text:
Why does the Pilatus PC 7 Mk II Altimeter show a decrease in altitude (~around 20-40ft) during takeoff roll, but recovers to original before unstick?
PC7 Mk II is equipped with digital ADC, how come this anomaly in altimeter readings during takeoff roll? Also, the pitot tube is situated well away from the prop wash and it has two static ports on either side for static balancing.

It suggests that both ports are seeing some drop in pressure, possibly due to fuselage contours just ahead of them, and only when the propeller wash velocity is high relative to the free stream velocity. Just spitballing...

@Johnk, but if the Px is dropping, the Alti would show an increase in reading rather than decrease.

Oh yeah. In that case, the opposite lol.

What is the location of the static ports?

@AeroAndy, Static Ports located in aft fuselage (flushed with surface), well clear of wing trailing edge ~ 4-5 ft aft... on both sides (for static balancing)

Thanks, @tata_sumo. I wanted to post an answer but but… probably a hypothesis does not qualify. Very low speeds with high propeller rpm settings result in a corkscrew or spiraling rotation to the slipstream. “At high propeller speeds and low forward speed (as in takeoffs and approaches to power-on stalls), this spiraling rotation is very compact and exerts a strong sideward force on the aircraft’s vertical tail surface.” p. 5-31 of FAA-H-8083-25C

My guess is one of the static ports is picking up some total pressure component due to an unusually high sidewash angle at that aft location.

On Raptor, for example, using differential pressure (left-right) to determine sideslip angle was not calibratable beyond about 30 deg of sideslip angle. Point being, an average L-R pressure would have some error in it, also.

@AeroAndy, your guess agrees with the anomaly's vanishing when the airplane is rolling fast, stretching the spiral farther aft (from the airplane's point of view).